The invention relates to the re-refining of used motor oil.
Extensive work has been reported in the patent literature on use of large amounts of hot, high pressure hydrogen for vaporization of used motor oil (UMO). While such processes are certainly technically feasible, there are significant capital costs associated with the relatively high pressure operation reported (typically 500 psig). Operation at high pressure makes it difficult to vaporize the used lube oil components, so higher hydrogen addition/circulation rates are used to facilitate vaporization, with hydrogen circulation rates of 10,000-18,000 SCFB being reported. Hydrogen helps suppress some condensation coking reactions that otherwise could occur in the heating and vaporization step. The hydrogen is also present in an amount sufficient to supply the hydrogen demand of a downstream hydrotreating reactor. This combination, high-pressure hydrogen coupled with downstream hydrotreating, can produce a liquid product from a UMO fraction which is excellent for use as either a lube stock or as cracker charge.
Representative hot hydrogen: UMO processes are listed below:
While this approach is excellent in terms of product quality, the capital and operating expense of such an approach are significant.
We devised a vapor vaporization process that, although it does not do as much as the high-pressure, hydrogen gas process, costs significantly less to build and operate. Our vapor vaporization process does not hydrogenate the UMO to any significant extent. The capital and operating costs are low because the process operates at relatively low pressures, ranging from atmospheric to 10 atmospheres.
We devised several related vapor vaporization processes using:
high heat content vapor (e.g. methane, ethane),
low pressure hydrogen,
steam
Accordingly the present invention provides a process for direct contact heating and vaporization of a UMO liquid hydrocarbon feed comprising lube oil boiling range hydrocarbons comprising heating a compressed recycled vapor in a heating means to produce a superheated vapor having a temperature sufficiently high to vaporize, at the conditions employed in said UMO vaporization process, at least a portion by weight of the distillable, lube oil boiling range hydrocarbon components in said UMO heating and vaporizing at least a portion of said UMO by direct contact of said UMO liquid feed with said superheated vapor in a UMO vaporization vessel operating at UMO vaporization conditions to produce a UMO vaporization vessel overhead vapor (OHV) fraction comprising vaporized UMO components and said superheated vapor and a UMO bottoms fraction comprising unvaporized UMO cooling said UMO vaporization vessel overhead fraction in a product recovery section comprising a cooling means at OHV condensation conditions including a temperature sufficiently low to condense at least a majority of the lube oil boiling range hydrocarbon components in said OHV fraction to produce a condensed liquid hydrocarbon fraction containing lube oil boiling range components as a liquid product of the process and a vapor fraction containing essentially all of said injected superheated vapor, exclusive of solution losses, if any compressing said recovered vapor fraction from said product recovery fraction to produce a compressed, recycle vapor fraction recycling said compressed vapor to said heating means of step a); and wherein said vapor, pressure and temperature in said UMO vaporization and cooling are selected to effect UMO vaporization, and condensation without hydrogenation of said UMO.
In another embodiment the present provides a heat pump, direct vapor injection, UMO vaporization process comprising heating vaporizing a liquid UMO liquid hydrocarbon feed by direct contact with a superheated vapor in a UMO vaporization vessel operating at UMO vaporization conditions to produce a UMO vaporization vessel OHV fraction comprising vaporized UMO components and said superheated vapor and a UMO bottoms fraction comprising unvaporized UMO cooling said OHV fraction in a cooling means to a temperature sufficient to condense at least a majority of normally liquid hydrocarbons present in said OHV, and wherein said cooling conditions include a temperature above ambient temperature recovering a vapor fraction above ambient temperature from said cooling separating means and heating said vapor by compressing same to form a compressed, pre-heated vapor superheating said compressed, pre-heated vapor in a fired heater or by indirect heat exchange to produce a superheated vapor stream; and recycling said compressed, superheated vapor to said UMO vaporization vessel.